Nitrogen release during reaction of coal char with O 2, CO 2, and H 2O

Abstract

The chemistry of char-N release and conversion to nitrogen-containing products has been probed by studying its release and reactions with O 2, CO 2, and H 2O. The experiments were performed in a fixed bed flow reactor at pressures of up to 1.0 MPa. The results show that the major nitrogen-containing products observed depend on the reactant gas; with O 2, NO, and N 2 being the major species observed. Char-N reaction with CO 2 produces N 2 with very high selectivity over a broad range of pressures and CO 2 concentrations, and reaction with H 2O gives rise to HCN, NH 3, and N 2. Observed distributions of nitrogen-containing products are little affected by pressure when O 2 and CO 2 are the reactant gases, but increasing pressures in the reaction with H 2O results in the formation of increasing proportions of NH 3. Formation of NH 3 is also promoted by increasing concentrations of H 2O in the feed gas. The results suggest that NO and HCN are primary products when O 2 and H 2O, respectively, are used as the reactant gases, and that the other observed products arise from interactions of these primary products with the char surface.